MAC OSX - Keystroke listener

OSX - keystroke listener and windows activate

    // listen for keystrokes
    [NSEvent addGlobalMonitorForEventsMatchingMask:NSKeyDownMask handler:^(NSEvent *event)
    {
        NSLog(@"%lui -- %@", (unsigned long)[event modifierFlags], event.characters );

        //
        // if flag and char do something, like bring to front the application
        // 256 is ESC, in my case.
        //
        if ( [event modifierFlags] == 256 && [[event charactersIgnoringModifiers] compare:@""] == 0 )
        {
            NSLog(@"-------- IN --------");
            [NSApp activateIgnoringOtherApps:YES];
        }
    }];